Mechanical seal

ABSTRACT

An improved mechanical seal of the type useful to form a seal between a stationary housing and a rotatable shaft. The seal comprises a rotatable seal element and a stationary seal element. There is an elastic element which forces the rotatable and stationary seal elements to sealingly engage. The mechanical seal can comprise removable clips to connect the seal to the housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to mechanical seals, and more particularlyhaving an improved mechanical seal having an elastic element and amechanical seal having an improved means to secure the seal to a machinestationary housing.

2. Description of the Related Art

A mechanical seal provides a seal between a rotatable element, typicallya shaft, and a stationary housing of an apparatus, typically containingfluid. Such seals are often associated with a fluid pump having a shaftextending through a pump housing wall. The pump shaft can be coupled toa motor through a motor shaft. The mechanical seal forms a seal betweenthe pump shaft and the outer surface of the pump housing. Mechanicalseals for such applications are commercially available and are describedin U.S. Pat. Nos. 4,639,000; 4,832,351, 4,989,882; and 4,993,720. Suchseals endure rigorous environments and last for extended time periods.

Seals which are known in the art comprise rotatable components andstationary components which contact to form a seal at opposing sealingsurfaces. The rotatable components include a shaft attachment means.Such a means is typically a sleeve having an inner perimeter surfacewhich sealingly fits over the outer perimeter surface of the shaft andis connected to the shaft by connecting means such as set screws. An "O"ring typically provides a seal between the shaft and the sleeve. Thereis a rotatable circumferential seal element interconnected to the sleeveso as to rotate when the shaft and sleeve rotate. The sleeve extendsaxially along the shaft.

The stationary components comprise a gland which extendscircumferentially around the shaft. The gland abuts against the outerhousing surface around the shaft. There is typically a sealing gasketinterconnected to the gland and located between the gland and thehousing. The gland functions as a base by which the seal is attached tothe housing. The connection is typically accomplished by bolts extendingfrom the outer housing wall. The bolts pass through slots or connectingextensions extending radially from the gland through the connectingslots or connecting extensions and secured with nuts. A stationary sealelement is located between the inner circumferential surface of thegland facing the shaft (i.e. the gland inner surface) and the shaft. Thestationary seal is directly or indirectly connected to the stationarygland. There are suitable means such as described in U.S. Pat. Nos.4,832,351 and 4,989,882 to axially center the various stationaryelements on the shaft. A circumferential spacing is maintained betweenthe stationary elements, and the shaft and various of the rotatingelements.

The stationary and rotatable components meet at opposing sealingsurfaces of the rotatable and stationary seal elements. There istypically a metal spring which forces either one of the seal elementstoward the opposing seal element to cause the opposing surfaces to bepressed together. The opposing seal element has restricted axialmovement and the surface of one seal element is forced by the springagainst the surface of the opposing seal element. Thereby, a seal isformed between the opposing sealing surfaces, i.e., the rotatable andstationary sealing elements.

Mechanical seals known in the art have at least one "O" ring associatedwith the sealing element being acted on, by the spring. The springforces this element toward the opposing element to form a seal. The "O"ring must form a seal not withstanding the axial movement and is knownas a "dynamic" "O" ring. Additionally, the dynamic "O" ring is locatedin an "O" ring slot which can clog. The spring must therefore provideforce to cause the sealing elements to come together under sufficientpressure to form a seal while overcoming the resistance of the dynamic"O" ring and clogging in the area of the dynamic "O" ring. It would bedesirable to eliminate the dynamic "O" ring as well as the metal spring.

Additionally, the means to connect the mechanical seal to the housing isintegrated into the structure of the stationary components. Themechanical seal is often set in place and removed in the small spacebetween the pump and motor. The means to attach the seal take up spaceand make access to the mechanical seal difficult for both installationand removal. A design with easier access to the seal elements at thelocation where the shaft extends from the housing is desireable.

SUMMARY OF THE INVENTION

The improved mechanical seal of the present invention includes anelastic spring element of the type useful to force a rotatable sealsurface into sealing contact with a stationary seal surface.Additionally, the mechanical seal can be connected to a machine housingusing removable clips to enable easier access for installation,maintenance and repairs to the mechanical seal and machinery to which itis attached, particularly in restricted spaces.

The mechanical seal of the present invention is useful to form a sealbetween a stationary housing and a rotatable shaft having a shaft axis.The shaft has a shaft surface having a shaft perimeter and extendsthrough an opening in the housing. The housing has an inner surface andan outer surface.

The mechanical seal comprises rotatable components and stationarycomponents. The rotatable components are interconnected to the shaft androtate with the shaft. The stationary components are interconnected tothe housing and do not rotate. The rotatable components and stationarycomponents are positioned relative to each other so that a rotatableseal surface sealingly engages a stationary seal surface. Such amechanical seal is particularly useful to form seals on machines whichhave rotatable shafts extending therefrom and fluid inside such as fluidpumps, i.e., water pumps.

In a preferred embodiment the rotatable components comprises a sleevehaving a shaft side inner wall. The inner wall has inner perimeter whichfits over the outer perimeter of the shaft. A radial wall extends fromthe inner wall of the sleeve. A rotatable circumferential seal elementis interconnected to the sleeve. The rotatable seal element has arotatable seal surface.

In a preferred embodiment the rotatable component further comprises arotatable chamber defined by the shaft side inner wall, the radial walland a circumferential outer wall. The outer wall extends from the radialwall over at least part of the shaft side inner wall and has openings.The rotatable circumferential seal element is located in the rotatablechamber with the rotatable seal surface facing the stationary sealsurface. Where the chamber is in communication with the fluid in thehousing, the fluid communicates into the rotatable chamber through theopenings.

A circumferential elastic element of the present invention is locatedaround the sleeve between the radial sleeve wall and the rotatable sealelement. The elastic element is an elastic, preferably elastomeric,sealing spring having an inner side adjacent to the sleeve inner wall, aradial wall side adjacent to the sleeve radial wall, a seal sideadjacent to the rotatable seal element and disposed to engage and forcethe rotatable seal element axially away from the radial wall and towardthe stationary seal element, and an outer side opposite the inner side.The outer side has an outer seal side surface extending for at leastpart of the circumference of the elastic element. The outer seal sidesurface extends angularly for at least part of the axial distance fromthe outer side surface at the seal side toward the inner side.

Preferably, the outer side of the elastic element has an outer radialside surface extending for at least part of the circumferential elementand extending angularly from the outer side at the radial side towardthe inner side. Preferably, the elastic element outer seal side surfaceand outer radial side surface form a circumferential groove in the outerside. More preferably, the outer side grooves have cross-sectionalshapes selected frown the group consisting of "U" and "V".

It is preferred that the forces exerted by the elastic spring element atthe radial wall side and at the seal side be relatively uniform acrossthe respective surfaces. In order to compensate for the groove in theouter side surface there can be at least one and preferably twocircumferential inner side grooves in the inner side of the elasticelement. Preferably, the outer side groove and the inner side groovehave a combined radial dimension at least equal to the radial length ofthe elastic element (distance from inner side to outer side). Thisenables the hydraulic forces to act in a balanced manner along the wholeradial length of the elastic element.

In certain embodiments addition elastic force can be provided by aspring means to force the outer seal surface toward the rotatable seal.The spring means can also force the outer radial surface toward theradial wall. The preferred springs are circumferential washer ringshaving a major plane at a greater angle to the radial plane of theelastic than the seal side surface and radial side surface. The washeris able to force the seal side of the elastic element toward theadjacent seal element.

The stationary components comprise a gland extending around theperimeter of the shaft. The gland has a gland component which cansealingly abut against the housing around the shaft. A stationarycircumferential seal element is interconnected to the gland. Thestationary seal element has a stationary seal surface. The gland islocated on the shaft at a position whereby the stationary seal surfaceopposes the rotatable seal surface.

The present invention also includes an improved mechanical sealcomprising connector clips having interconnect means to be removablyconnected to the stationary components of the seal and means tointerconnect to the housing. Preferred interconnecting means toremoveably connect the stationary components to the connector clips areopposing pins and slots to receive the pins in respective stationarycomponent and clips. The means to interconnect to the housing are slotsto receive bolts connected to and extending from the housing.

The present invention also includes an elastic sealing spring having aninner side, a first radial side, a second radial side and an outer side.The outer side has a circumferential groove having a first surfaceextending angularly from the outer side toward the inner side and asecond surface extending from the outer side angularly toward the innerside. As indicated above, there can be a spring element adjacent to atleast one of the first surface and second surface of the outer side toforce at least one of said first outer side toward the first radial sideand said second outer surface toward the second radial side. It isrecognized that this elastic spring can be used to force the stationaryseal element toward the rotable seal element or the rotatable sealelement toward the stationary element. The latter is preferred since theelastic element can eliminate an "O" ring on the rotational sealelement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial section view of a preferred embodiment of themechanical seal of the present invention on a shaft connected to ahousing.

FIG. 2 is an end view of the embodiment shown in FIG. 1.

FIG. 3 illustrates a preferred stationary seal subassembly.

FIG. 4 is an alternate embodiment used to illustrate the elastic elementof the present invention.

FIG. 5 is a sectional view of the elastic element of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be understood by those skilled in the art byreference to the accompanying FIGS. 1-5 which illustrate preferredembodiments.

The preferred mechanical seal is shown forming a seal on an apparatus,such as a pump, between a stationary housing 10 and a rotatable shaft 14having a shaft axis 18. Housing 10 has inner surface 11 and outersurface 12. The shaft 14 has a shaft perimeter 20 and extends through anopening 22 in the housing 10.

The mechanical seal comprises rotatable components 26 in a rotatableassembly and stationary components 30 in a stationary assembly. Therotatable components 26 are interconnected to shaft 14 by suitable meansand rotate with the shaft 14. The stationary components 30 areinterconnected to the housing 10 and do not rotate. The stationaryassembly of components arid rotatable assembly of components arepositioned relative to one another to meet at respective seal surfaces,i.e. a rotatable seat surface and a stationary seal surface to form amechanical seal.

The rotatable components 26 include a sleeve 34. The sleeve 34 has ashaft side inner wall 36 which has an inner surface having an innerperimeter 38 which fits over the outer perimeter 20 of the shaft 14. Thesleeve 34 preferably has a radial wall 40 which extends from the innerwall 36. A rotatable circumferential seal element 44 is interconnectedto the sleeve 34 in order to rotate. Element 44 can be connected tosleeve 34 by any suitable means such as a pin or opposing slots andextensions in the sleeve and element 44. Preferably, sleeve 34 hasextensions 45 which mate with opposing grooves 46 in element 44. Therotatable seal element 44 has a rotatable seal surface 48. The sleeve 34can have suitable means by which it can be secured to the shaft 14. Suchmeans include set screws (not shown) which can pass through threaded setscrew holes. Additionally, there can be a collar 41 having holes throughwhich the set screws pass and which can also be secured in place by theset screws. The various elements of the rotatable and stationarycomponents can be maintained in place between stationary collar 41 andradial wall 40.

The stationary assembly components 30 include a gland 52 which extendsaround the perimeter 20 of the shaft 14. The gland 52 has a glandcomponent, such as gland gasket 54 located in circumferential glandgasket slot 55. The gland gasket can sealingly abut against the housing10 around the shaft 14. A stationary circumferential seal element 56 isdirectly or indirectly interconnected to the gland 52 by suitable meanssuch as at least one pin or opposing slots and extensions in the gland52. The stationary seal element 56 has a stationary seal surface 58. Thegland 52 is located on the shaft 14 at a position whereby the stationaryseal surface 58 opposes the rotatable seal surface 48. The gland 52 canbe axially centered around shaft 14 using spacer means 53. The spacermeans 53 cam be made of a suitable material such as carbon filledpolytetrafluoroethylene or carbon filled phenolic resin.

A preferred stationary seal element 56 assembly is shown in FIG. 3 anddescribed in U.S. Pat. No. 4,832,351, hereby incorporated by reference.Briefly, the stationary seal element 56 has a stationary seal extension57 opposite the stationary seal surface 58. The extension slideably fitsinto stationary support ring 59 slot 60. There are floating "O" rings 61between the extension 57 and the inner walls of the slot 60. A hydraulicmedium such as silicon gel is located in the slot cavity 62 between theend of the extension and the bottom of the slot 60. A stationary sealsuch as "O" ring 63 is located between the support ring 59 and gland 52.Thereby, the stationary seal element 56 is self-aligning arid is axiallystable. The seal element 56 can be attached to support ring 59 bysuitable means such as pin 65. The support ring 59 remains stationary bysuitable means to be attached to gland 52, but is preferably maintainedstationary by the friction between "O" ring 63 and gland 52.

A circumferential elastic element 64 is located around the sleeve 34between the radial sleeve wall 40 and the rotatable seal element 44. Theelastic element 64 has an inner side 66 adjacent to the sleeve innerwall 36, a radial wall side 70 adjacent to the sleeve radial wall 40,and a seal side 74 adjacent to the rotatable seal element 44. Theelastic element 64 is positioned to sealingly engage and force therotatable seal element 44 axially away from the radial wall 40 andtoward the stationary seal element 56. There is an outer side 78opposite the inner side 66. The outer side 78 has an outer seal sidesurface 82 extending for at least part of the circumference of theelastic element 64. The outer seal side surface 82 extends angularly forat least part of the axial distance from the outer side 74 at the sealside toward the inner side 66. Preferably, the elastic element 64 has anouter radial side surface 88 extending for at least part of thecircumference of the elastic element 64. The outer radial side surface88 extends angularly from the outer side 78 at the radial side 70 towardthe inner side 66.

In the particularly preferred embodiment illustrated in FIG. 1, therotatable component assembly further comprises a rotatable chamber 90defined by the shaft side inner wall 36 of sleeve 34, the radial wall 40and a circumferential outer wall 94. The outer wall 94 extends from theradial wall 40 over at least part of the shaft side inner wall 36. Thereare openings 98, preferably in the outer wall 94 to permit fluid frominside the apparatus housing to communicate with the outer side 78 ofthe elastic element 64. The elastic element 64 is tightly squeezedbetween radial wall 40 and the rotatable seal element 44. The pressureof the fluid acting on outer seal surface 82 and preferably also outerradial side surface 88 also forces the axial floating rotatable sealelement 44 into a sealing contact with the stationary seal element 56 attheir respective seal surfaces 48 and 58.

The outer seal side surface 82 and outer radial side surface 88 in theouter side 78 of the elastic element 64 preferably define acircumferential groove 102 in the outer side 78. The groove preferablyhas cross-sectional shapes selected from the group consisting of "U" and"V" as shown in FIGS. 1, 4 and 5.

It is desirable to have uniform pressure on radial wall side 70 and sealside wall 74. In order to accomplish this, particularly, where there isa groove 102 in the outer side 78 of the elastic element 64, there is atleast one circumferential inner side groove 106 in the inner side 66.More preferably, there are two circumferential grooves 106 extendingradially into the inner side 66.

The elastic element 64 can further comprise a spring means to force theouter seal surface 82 toward the rotatable seal 44. The spring means canalso force the outer radial surface 88 toward the radial wall 40. Usefuland preferred spring means can include angular washers 110 and 110' toforce onto outer seal surface 82 and optionally outer radial sidesurface 88 as shown in FIG. 4. Alternatively, a circumferential springelement having a similar shape to groove 102 and angled toward walls 70and 74 to force surfaces 88 and 82 toward those walls can be used. Byangled it is meant that angle "x" and "y" of surfaces 82 and 88 are lessthat corresponding angle "x" and "y" of the adjacent spring surfacesbefore the springs 110 are forced into the groove 102.

The mechanical seal of the present invention can be connected to form aseal between a stationary housing 10 and a rotatable shaft 14 having ashaft axis 18 where the shaft 14 extends through an opening 22 in thehousing 10. Typically, there are studs or bolts 112 extending from andinterconnected to the housing wall. The extending ends can be threadedto received a nut 114. Typically, there are from two to eight and moretypically two to six bolts extending. The gland 52 can have slots orholes to receive the bolts 112. The bolts pass through the gland 52. Thegland 52 along with the mechanical seal are secured sealingly in placebetween the housing 10 and the nuts 114.

In a specific and preferred embodiment of the present invention themechanical seal further comprises a plurality of connector clips 120removably interconnected to a stationary component, preferably gland 22.The connection can be a tongue and groove or pin in a hole or slotconnection. Preferably each clip 120 has a pin 122 which fits into acorresponding hole or slot 124 in the gland 22. Alternatively, the pincan extend from the gland 22 and the slot can be in the clip 120. Theclip 120 can then be put in place after the seal is installed andremoved prior to conducting maintenance or removal of the seal. The clip120 can have means to attach to the housing such as slots 126 throughwhich bolts 112 can pass and be secured by nuts 114. and means tointerconnect to the housing.

The various elements of the seal of the present invention can be made ofsuitable materials to withstand the environments and conditions whichmust be encountered. Typically, commercially available elastomeric "O"rings can be used. The sleeve 14, gland 22, support ring 59, collar 41and other related parts can be made of metal, preferably steel and mostpreferably stainless steel. One of opposing seal elements, eitherrotatable seal 44 or stationary seal 56 is a hard surface made of amaterial such as silicon carbide while the other is a soft surface suchas carbon. Preferably, the rotatable seal 44 is made of carbon and thestationary seal 56 is made of silicon carbide. The elastic element 64can be made of a suitable elastomeric material or composite. The baseelastomer can be made of chloroprene, nitrile rubber, EPDM or the like.

The mechanical seal of the present invention can be adapted to virtuallyany size shaft but can typically be used and sized for shafts havingdiameters ranging from 0.5 to 12 and more typically 1 to 6 inches.

Although the invention is described by reference to a particularillustrative embodiment, changes and modifications may be apparent tothose skilled in the art without departing from the spirit and scope ofthe invention. Therefore, all such changes and modifications arereasonably included within the following claims.

What is claimed is:
 1. An improved mechanical seal of the type useful toform a seal between a stationary housing and a rotatable shaft having ashaft axis, the shaft having a shaft perimeter and extending through anopening in the housing, the mechanical seal having rotatable componentsand stationary components,the rotatable components having a sleeve, thesleeve having a shaft side inner wall having an inner perimeter whichfits over the outer perimeter of the shaft and a radial wall extendingfrom the inner wall, and a rotatable circumferential seal elementinterconnected to the sleeve, the rotatable seal element having arotatable seal surface, the stationary components having a glandextending around the perimeter of the shaft, the gland having a glandcomponent which can sealingly abut against the housing around the shaft,a stationary circumferential seal element interconnected to the gland,the stationary seal element having a stationary seal surface, the glandlocated on the shaft at a position whereby the stationary seal surfacefaces the rotatable seal surface, wherein the improvement comprises: acircumferential elastic element located around the sleeve between theradial sleeve wall and the rotatable seal element, having an inner sideadjacent to the sleeve inner wall, a radial wall side adjacent to thesleeve radial wall, a seal side adjacent to the rotatable seal elementand disposed to sealingly engage and force the rotatable seal elementaxially away from the radial wall, and an outer side opposite the innerside, the outer side having an outer seal side surface extending for atleast part of the circumference of the elastic element, the outer sidehaving a single circumferential groove and the inner side having atleast one circumferential groove; and the rotatable component furthercomprising a rotatable chamber defined by the shaft side inner wall, theradial wall and a circumferential outer wall, the outer wall extendingfrom the radial wall over at least part of the shaft side inner wall andhaving openings.
 2. The improved seal as recited in claim 1 wherein theimprovement further comprises the outer seal side of the elastic elementhaving an outer radial side surface extending for at least part of thecircumferential element and extending angularly from the outer side atthe radial side toward the inner side.
 3. The improved seal as recitedin claim 1 wherein the circumferential groove in the outer side hascross-sectional shapes selected from the group consisting of "U" and"V".
 4. The improved seal as recited in claim 1 wherein there are twocircumferential grooves extending radially in to the inner side.
 5. Theimproved seal as recited in claim 1 further comprising spring means toforce the outer seal surface toward the rotatable seal.
 6. The improvedseal as recited in claim 5 wherein the spring means force the outerradial surface toward the radial wall.
 7. The improved seal as recitedin claim 1 with the circumferential elastic element of the outer sidecircumferential groove having a first surface extending angularly fromthe outer side toward the inner side and a second surface extending formthe outer side angularly toward the inner side.
 8. The improved seal asrecited in claim 7 further comprising a spring element adjacent to atleast one of the first surface of the outer side and second surface ofthe outer side to force at least one of said first surface toward thefirst radial side and said second surface toward the second radial side.9. A mechanical seal useful to form a seal between a stationary housingand a rotatable shaft having a shaft axis, the shaft having a shaftperimeter and extending through an opening in the housing, themechanical seal comprising rotatable components and stationarycomponents,the rotatable components comprising: a sleeve, the sleevehaving a shaft side inner wall having an inner perimeter which fits overthe outer perimeter of the shaft and a radial wall extending from theinner wall; a rotatable circumferential seal element interconnected tothe sleeve, the rotatable seal element having a rotatable seal surface;and a circumferential elastic element located around the sleeve betweenthe radial sleeve wall and the rotatable seal element, having an innerside adjacent to the sleeve inner wall, a radial wall side adjacent tothe sleeve radial wall, a seal side adjacent to the rotatable sealelement and disposed to sealingly engage and force the rotatable sealelement axially away from the radial wall, and an outer side oppositethe inner side, the outer side having an outer seal side surfaceextending for at least part of the circumference of the elastic element,the outer side having a single circumferential groove and the inner sidehaving at least one circumferential groove; and the stationarycomponents comprising: a gland extending around the perimeter of theshaft, the gland having a gland component which can sealingly abutagainst the housing around the shaft; and a stationary circumferentialseal element interconnected to the gland, the stationary seal elementhaving a stationary seal surface, the gland being located on the shaftat a position whereby the stationary seal surface opposes the rotatableseal surface.
 10. The seal as recited in claim 9 wherein the outer sealside of the elastic element has an outer radial side surface extendingfor at least part of the circumferential element and extending angularlyfrom the outer side at the radial side toward the inner side.
 11. Theseal as recited in claim 9 wherein the rotatable component furthercomprises a rotatable chamber defined by the shaft side inner wall theradial wall and a circumferential outer wall, the outer wall extendingfrom the radial wall over at least part of the shaft side inner wall andhaving openings.
 12. The seal as recited in claim 11 wherein there is acircumferential groove in the outer side.
 13. The seal as recited inclaim 12 wherein the elastic element grooves in the outer side have thecross-sectional shapes selected from the group consisting of "U" and"V".
 14. The seal as recited in claim 9 wherein there are twocircumferential grooves extending radially into the inner side.
 15. Theseal as recited in claim 11 further comprising spring means to force theouter seal surface toward the rotatable seal element.
 16. The seal asrecited in claim 15 wherein the spring means force the outer radialsurface toward the radial wall.
 17. The seal as recited in claim 9 withthe circumferential elastic element of the outer side circumferentialgroove having a first surface extending angularly from the outer sidetoward the inner side and a second surface extending form the outer sideangularly toward the inner side.
 18. The seal as recited in claim 17further comprising a spring element adjacent to at least one of thefirst surface of the outer side and second surface of the outer side toforce at least one of said first surface toward the first radial sideand said second surface toward the second radial side.